It's hard to read this, he might well be in hospital as a precaution, but we all know that if he was in a bad way, Downing Street would've run with the precaution story any way. From a political/PR standpoint, Johnson going to hospital is not what the government would've wanted, which leads me to believe it's worse than they're letting on, then again his doctor might have read the riot act and told him in no uncertain terms to go to hospital like right now.
Either way, it's worrying on a personal and political level.